project work phase 1

1 files changed, 72 insertions, 0 deletions

diff --git a/src/date.c b/src/date.c
new file mode 100644
index 0000000..7e6bc77
--- /dev/null
+++ b/src/date.c
@@ -0,0 +1,72 @@
+#include <time.h>
+
+#include <posthaste/date.h>
+
+ph_date_t date_from_string(const char str[static 11])
+{
+	unsigned year  = (str[0] - '0') * 1000
+	                 + (str[1] - '0') * 100
+	                 + (str[2] - '0') * 10
+	                 + (str[3] - '0');
+
+	unsigned month = (str[5] - '0') * 10
+	                 + (str[6] - '0');
+
+	unsigned day   = (str[8] - '0') * 10
+	                 + (str[9] - '0');
+
+	return date_from_numbers(year, month, day);
+}
+
+ph_date_t date_from_numbers(unsigned year, unsigned month, unsigned day)
+{
+	return year << 9 | month << 5 | day;
+}
+
+void date_split(ph_date_t date, unsigned *year, unsigned *month, unsigned *day)
+{
+	if (year) *year  = date >> 9;
+	if (month) *month = (date >> 5) & 0xf;
+	if (day) *day   = date & 0x1f;
+}
+
+void date_to_string(char str[static 11], ph_date_t date)
+{
+	unsigned year, month, day;
+	date_split(date, &year, &month, &day);
+
+	str[0] = '0' + (year / 1000) % 10;
+	str[1] = '0' + (year / 100) % 10;
+	str[2] = '0' + (year / 10) % 10;
+	str[3] = '0' + year % 10;
+	str[4] = '-';
+	str[5] = '0' + (month / 10) % 10;
+	str[6] = '0' + month % 10;
+	str[7] = '-';
+	str[8] = '0' + (day / 10) % 10;
+	str[9] = '0' + day % 10;
+	str[10] = '\0';
+}
+
+bool date_valid(ph_date_t date)
+{
+	unsigned year, month, day;
+	date_split(date, &year, &month, &day);
+
+	struct tm tm = {0};
+	tm.tm_year = year;
+	/* goddammit */
+	tm.tm_mon = month - 1;
+	tm.tm_mday = day;
+
+	time_t r = mktime(&tm);
+	/* if mktime fails to represent our time, it returns -1. mktime somewhat
+	 * curiously accepts dates outside regular ranges, like negative time,
+	 * but adjusts the tm structure to be 'correct', so we can check if any
+	 * of the times were modified to see if this is a valid time. */
+	if (r == -1 || (int)year != tm.tm_year
+	    || (int)month != tm.tm_mon + 1|| (int)day != tm.tm_mday)
+		return false;
+
+	return true;
+}